If the abstract doesn’t quite make sense to you, some context is that a “crossbar” is a very small circuit structure we can fabricate where one set of parallel wires crosses another set of parallel wires. A bit can be stored at each junction, so that the crossbar can act as an extremely high-density memory. Our group at HP has made wires as narrow as 6 atoms wide (2 nanometers wide). A problem we have with stuff this small is that there are sure to be defects in what we fabricate, and the paper is about a defect-tolerance technique — a way to make the crossbars such that they will work in spite of having a lot of defects present. The “demultiplexer” the paper talks about is a kind of digital circuit needed to select individual bits in the memory being accessed.